Flexible billing enables vendors to mix and match subscription fees, usage charges, one-time payments, and custom terms for different customers without requiring separate systems. It is essential for serving both SMB and enterprise segments with different billing expectations.

Example: A SaaS platform uses flexible billing to charge SMB customers a monthly flat fee, usage-based billing for API customers, and annual invoiced contracts with Net 30 terms for enterprise accounts, all managed from the same billing system.